1. Field of the Invention
The present invention relates to a vehicle headlight apparatus, which performs a swivel operation that changes an optical axis of a headlight in a horizontal direction correspondingly to a steering operation.
2. Description of Related Art
Conventionally, there has been proposed an adaptive front-lighting system (AFS) that radiates light in a direction, which a driver of a vehicle desires. The AFS is realized by changing a direction of radiation (i.e., an optical axis) of a headlight of the vehicle. The AFS includes a leveling mechanism and a swivel mechanism for changing a direction of the optical axis of the headlight. Here, the leveling mechanism vertically changes the direction of the optical axis, and the swivel mechanism horizontally changes the direction of the optical axis.
In the swivel mechanism of the above functions, a target swivel angle is computed based on inputted data, such as a headlight switch signal, a vehicle speed and a steering angle. Then, there is preformed an operation for driving an actuator that changes the optical axis of the headlight such that the optical axis corresponds to the target swivel angel. For example, in a case of a right turn, the optical axis of the headlight is changed to a right direction. Also, in a case of a left turn, the optical axis is changed to a left direction. Therefore, this improves the viewability in a vehicle drive direction at night travel (see Japanese Unexamined Patent Publication No. 2003-72460 corresponding to U.S. Pat. No. 6,778,892).
However, the conventional swivel mechanism has a disadvantage. The conventional swivel mechanism starts driving the actuator based on the headlight switch signal so that the optical axis of the headlight is changed to set at the target swivel angle at one stroke when the headlight is turned on during the vehicle travels on a curve. For example, here is supposed a vehicle, which has an automatic lighting apparatus for automatically lighting the headlight when a travel environment indicates a predetermined darkness. When this vehicle travels into a tunnel, which curves to the right, the headlight is automatically turned on, and simultaneously the optical axis of the headlight is widely moved to the right.